Factory Five Racing Forum banner

Status
Not open for further replies.
1 - 20 of 20 Posts

·
Senior Charter Member
Joined
·
1,966 Posts
Discussion Starter #1
Finally got the T-Bird SC rear clip completely taken apart (what a PITA) and cleaned up. Thanks Rodney for loaning me a few tools. Almost had to use the Sawz-All on that [email protected] T-Bird subframe!

Anyway, I've located a local guy to rebuild the 8.8 pumpkin who works for one of the Nascar Winston-Cup teams and used to work for Ford Motor Sport. So, needless to say, he knows his Fords.

I'm having him do a complete rebuild (seals, trac-loc, pinion bearing) on the 8.8 pumpkin and am trying to decide about gears. I have the 3.27 gears and trac-loc already and have been combing the archives late tonight for information. My plan is to run a stock donor 5.0 EFI with a T-5 for starters until the motor gives up then maybe progress to a stroker kit during the rebuild.

I find lots of people jumping from 2.73 and 3.08 gears to 3.55 gears with lots of success. But, I don't see the anyone touting a big difference or cost justification to go from 3.27 to 3.55

That said, I'm thinking about either going to 3.73 gears or just not changing the gear ratios at all. The car will be mainly be street driven on good weather weekends. While I'd like to carry on a conversation going down the highway (lower gears concern me with higher RPMs), I also want the Cobra to feel quicker than my daily driver M3 (0-60 in low-mid 5 secs).

Recommendations? I've thought about keeping what I have and trying it out, but since the differential is apart now is the time to decide.

Thanks for the input.

Drew
FFR????
 

·
FFCobra Craftsman
Joined
·
1,975 Posts
Drew - I would think that with a mostly stock mill and tranny, the 373's would give your beastie some real wheel smokin' ability. The 327's that it probably came with would be OK if you wanted to save some bucks. 273's are a waste. Maybe later on if you put some serious HP in the car you might want to think about 355's. If you go for new gears, do not use Richmond rear gears, go with Ford Racing.

Oh yeah, like you have to do...dis is yust mine vasser mit gasse.

Frank.
 

·
FFCobra Fanatic
Joined
·
2,575 Posts
Drew,
I put 3.27's in my IRS from the start. Don't regret a bit of it either. My engine is mildly putting about 350hp/crank and the gears suit it fine. I also have the stock T5 tranny.

When starting the project I did a lot of research on what gears to use. Most at the time were using 3.55's. When I spoke with FMS, it was suggested to go to the 3.27's for better all around driving. Now the fun part.

When you use the 3.27 ratio, the engine will not be as effiecient in the higher gears at the posted speed limit. The engine is most efficient running around 2400rpm. The 3.27's will run at 2800rpm at 70mph in 4th gear and 2200rpm at 70mph in 5th gear. The 3.55's will run at a higher rpm in each of these giving you a good higher end rpm band.

Now, when you use the lower gears the reverse happens. The 3.27's will carry out more speed in each gear. I carry 40+ in 1st, 75+ in 2nd, 120+ in 3rd and don't know what 4th or 5th will do (don't want to try either). So, if you want low end driveability and performance I'd go the 3.55's and not worry with the stock engine setup. You can smoke more rubber with the 3.55's but you don't go anywhere when you do this. ;)

However, if you plan on putting some uuummmffff under the hood, I think you'd be better off with the 3.27's. jmo
 

·
Registered
Joined
·
1,378 Posts
If your looking for fun and being a street car, use the 3.27s; the weight of these cars will help us out a great deal more than the donors... 3.55s would be fun, but not altogether THAT noticable except if your using street tires (smokey launches). 3.73s (IMO) should be reserved for competition duty.
 

·
Senior Member
Joined
·
7,097 Posts
So what I'm getting from you guys, is that the 3:73's I'm putting into mine may be too much for just street use? I got them for free so I think that weighs in on the decision.
 

·
Registered
Joined
·
628 Posts
I don't think 3:73s are to much for the street. Actually , I like them for the street. Real short 1st gear, but great all around performance.

For the track they are to much of a ratio. I have em and would like to drop to 3:55s. I have a Tremec with .8 fifth gear, and I run out of rpms in fifth pretty quick on any track with a reasonable straight.

I'm not sure about Earl's numbers but I was bumping 140 in fifth @ the Glen last weekend just below 6 KRPMs.

Hank
FFR 1776-II
 

·
Registered
Joined
·
1,378 Posts
Mike, 3.73s are fun gears! IMO they aren't really necessary if the car is going to see virtually all street duty. I'd have 3.73s if using stickies for quarter mile duty. I think you'll spend a lot of time spinning street rubber in the first 2 gears with 3.73s. RPMs at 80mph might get a little tiresome as well...
I ran 4.10s for years because they were so much fun, but my car weighed almost DOUBLE that of these cars. It needed all the help it could get to start rolling... then again I had a 6sp.
 

·
Registered
Joined
·
1,378 Posts

·
FFCobra Fanatic
Joined
·
820 Posts
i went from 3:73 to 3:27 and loved it. i like highway driving and don't like the high RPMs in 5th. i just bought a car with 2:73 and it should get here next week. i have a set of 3:08 lined up for it.

just my .02

luis lopezFFR1584
 

·
Premium Member
Joined
·
4,703 Posts
I like my 373 gears I don't have to 80 to shift into 5th. Smok'em up whenever I like.
 

·
Registered
Joined
·
304 Posts
Drew...... It probably depends on how much freeway driving you will do with the cobra. I started out with the 308's, great low rpm on the highway but too slow off the line. Then I put in a turbocoupe rear with 355's. Much,much better! (However, rpm's went up a fair amount at 80mph on freeway.) Gears were a little beat, so I swapped in 373's. Great off the line, and for tooling around town and countryside.

So, if you want to drag and do little freeway time, slap in those 373's. You are pretty much in the power band ALL the time,even on the freeway @70-80mph. But, if you have to live on the interstate, keep the 327's. JMHO, Scott
 

·
Charter Member
Joined
·
215 Posts
In all probability if you have the 5.0 production engine the 3.55 would be best. However, if you have more horsepower, let's say 325 plus horses, the 3.27 would be the best selection. More horseys with 3.55 gears or greater (3.73) all you're going to do is "SMOKE 'EM" or burn some clutch to keep it from spinning those expensive tires. This car has no weight in the rear end. And only a few guys have quality suspension systems for a great "hook-up" on acceleration.
 

·
Senior Charter Member
Joined
·
599 Posts
Drew,

Originally, I had the 3.27 rear gears then I switched to the 373's which are much better. My motor produces 437 hp on the dyno. With a .68 fifth gear, my rpms are now 2200 @ 65 mph and 3350 @ 100 mph. I believe these rpms to be much better now than with the 327's. She pulls noticably stronger throughout the rpm range with the 373's than she did with the 327's.

Last winter, we pulled the 355's out of Rob's FFR and put in 410's. His motor is making approx. 270-275 hp. I'm not certain of his rpms at 65 mph but at 100 mph they're 3500. At first, he was reluctant to go with the 410's but now wishes he'd gone steeper yet.

Stock 5.0L motors are best with at least 373's if you want greater acceleration. With 437 hp my FFR will spin it's tires in first and second if I simply stand on it. It will not spin them in third or higher and neither will Rob's.

In fact, another local FFR who claimed he could smoke'm in second gear never could while I was witness. He had a stock 5.0L with 3.08 gears. Read the discussion about how fast we've all driven our FFR and you'll see a very limited response from those who claim to have driven over 151 mph. It's one thing to claim something and often quite another to verify it.

Go with the 373's.

All the best,
Bob
 

·
Registered
Joined
·
1,059 Posts
I had the same question a year ago. Looking at all the responces, I noticed that everyone with 373 liked them but said first gear was short. After driving all four geared cars,(273 included) I'd say first is non existent in daily driving. 20 to 30 MPH shift is a bit soon.
Look at Weendogs numbers for the 327's and remember your planned use for the car.

I have 355's in the Cobra and love it. But it gets you out of first real quick in normal daily driving.
I am going with 327 for the Coupe.

Hope it helps
Brad

 

·
Senior Charter Member
Joined
·
1,966 Posts
Discussion Starter #16
Thanks for the insights guys. Since this is going to be my weekend car (toy according to the wife), the higher 3.73 gears sounds like a feasible and cheap performance modification(relative to engine mods) to get faster acceleration on a stock 5.0 engine. I would guess that <30% of my driving time will be spent on the interstate, so I'll just have to tolerate the higher rpms when on the interstate.

While I was really hoping for some concensus on the ratios, it seems like many people find that the 3.73 cause the car to spin the tires, but I presume from your comments in that this only happens if you press the accelerator all the way to the floor.

So, I'll probably get my mechanic to install the 3.73s, but I'll keep the 3.27s if I ever want to swap back should I do a stroker motor build down the line.

His price for the 3.73s is about $175 for FMS products, which is about $25-$30 higher than most places but I guess its worth it as he'll warranty it with his own parts.

Drew
FFR????
 

·
Registered
Joined
·
2,490 Posts
Go with the 3.27's. If you want to accellerate quick just shift later. That way you have a 4 speed with an overdrive. With 3.73 you're wasting first gear and so only have a 3 speed with an overdrive. If you just have to change the gears then 3.55 would be preferable.
 

·
Senior Charter Member
Joined
·
540 Posts
you need to consider the type of first gear you have in your tranny. If the tranny is a stock t-5 it probably has a 3.35:1 first gear then you will like the 3.27 or 3.55 rear gear. If you have a 2.95:1 first gear then you will like the 3.73 rear gears
 

·
FFCobra Fanatic
Joined
·
958 Posts
My Mazda pickup has 3.73's and my E-150 van has 3.55's. They're not hotrods but I often start out in 2nd gear (5 spd's) with either on a level or downhill street just to avoid shifting right away. Even on these heavy vehicles, 1st is a little short.
 
1 - 20 of 20 Posts
Status
Not open for further replies.
Top